Railway traffic controlling apparatus



Jan. 5, 1937. E ALLEN ET AL 2,066,993

RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Jan. 16, 1955 Earl M. Allen and y Henry 5. Young.

THEIR A TTORNEY Patented Jan. 5, 1937 PATENT ()FFICE RAILWAY TRAFFIC CONTROLLING APPARATUS Earl M. Allen, Swissvale, and Henry S. Young,

Wilkinsburg, Pa.,

assignors to The Union Switch & Signal Company, Swissvale, Pa, a corporation ,of Pennsylvania Application January 16,1935, Serial No; 2,076

19 Claims.

Our invention relates to railway traffic controlling apparatus, and in particular, to approach locking apparatus for preventing the operation of a track switch when a signal governing the movement of traflic over the switch has been cleared, and also for a selected time interval after such signal has been manually restored to stop under certain trafiic conditions, so that if an approaching train is unable to stop without over-running the signal, the switch will remain locked, the switch becoming locked due to the occupancy of the switch section by the train in that case before the approach locking can be released.

One object of our invention is to provide means for shortening the time interval imposed upon the release of the locking when the signal which is manually put tostop is a slow-speed signal, in which case the speed of the approaching train will be relatively low.

Another'object of our invention is to provide a single time measuring device so arranged that either a relatively long or relatively short time element may be imposed, depending upon whether the signal that is restored to stop is for governing high speed or slow speed traffic movements.

We will describe two forms of apparatus embodying our invention, and will then point out the novel features thereof in claims.

Referring to the accompanying drawing, Fig. 1 illustrates one form of apparatus embodying our invention, while Fig. 2 illustrates a modification of a portion thereof arranged for the control of a train-order signal.

Similar reference charactersrefer to similar parts in both views.

Referring to Fig. 1, the diagram at the top represents a stretch of railway track comprising a switch section IT containing a track switch I and an adjacent approach section AT. Each section is provided with the usual closed track circuit including a normally energized track relay as indicated diagrammatically in the drawing, these track relays being designated ATR and ITR, respectively.

The movement of traflic into section IT in the normal direction from left to right is governed by a signal R2 comprising a. high speed arm a" cupied by a preceding train. The movement of traffic into section IT against the normal direction of traffic is governed by the slow speed signal L2. A distant signal RD for governing traffic approaching section IT is located a suitable distance in the rear of signal R2, and it is to be understood that in accordance with the usual practice signal RD normally indicates caution, or proceed, prepared to stop at next signa and is cleared to indicate proceed only when arm a of signal R2 has been cleared to indicate caution or proceed.

The arms a and c of signal R2 are controlled by signal relays RAZH and RCZI-I, respectively, and signal L2 is controlled by a signal relay L2H. The local signal control circuits are not shown in detail, but it is to be understood that each signal arm will be cleared when the corresponding signal relay is energized, and will indicate stop when its signal relay is deenergized. Relays RAZH and RCZH are selectively controlled,

through the medium'of a lever repeating relay RZVR and an auxiliary relay CZVS, by a manually operable signal lever RZV, which as shown in the drawing is in its normal position n to. which it is moved to cause signal R2 to indicate stop. Lever RZV has three positions and may be moved to position 1' to clear arm a or to position I to clear arm 0 of signal R2.

Switch I is actuated by a power operated switch machine ISM controlled in the usual manner, as indicated diagrammatically in the drawing, by a polarized switch control relay IWR, which in turn is controlled, when traffic conditions are favorable for the operation of the switch, by the contacts of a switch lever IV in such a manner that switch I will be moved to its normal position as shown in the drawing when lever IV is moved to position n and will be reversed when the lever is moved to position 1'.

Switch-machine ISM is provided with the usual indication circuit controller for controlling indication relays INKR and IRKR as indicated in the drawing, relay INKR being energized only when switch I is closed and locked normal, while relay' IRKR is energized only when the switch is closed and locked reverse.

Associated with signal R2 there is an approach locking stick relay RMR which becomes deenergized to lock the switch by opening a contact in the circuit for relay IWR when either arm a or c of signal R2 is cleared. When signal R2 is put to stop, relay RMR may be energized over a pickup circuit which has a plurality of branches, one of which includes a back contact 3 of track relay ITR closed when signal R2 is put to stop automatically by a train passing the signal and entering section IT. Another branch includes a front contact A of relay ATR closed when approach section AT is unoccupied, while other branches include contacts of a time-element device TE and of a slow-acting relay TEP, associated there with.

The time element device TE may be of any suitable type, but as herein illustrated is to be understood as being of the clockwork type as disclosed in the Neubert 8; McClelland Patent No. 992,236, issued May 16, 1911, but arranged as shown in the Manrodt Patent No. 1,916,485, issued July 4, 1933, to have a contact 5 closed when the control knob is reversed manually to wind up the spring motor, and two other contacts 6 and 7 closed after the knob is released and the clockwork mechanism has been driven by the spring motor for different predetermined times during the return of the contacts to their .normal position.

In order to simplify the drawing, we have shown relay contacts which in some instances are not adjacent the respective relays which operate them, but in each case such contacts bear the reference characters identifying the respective relay as well as a number identifying the contact. Thus the branch of the pickup circuit for relay RMR which includes contact 5 of the time element device TE includes a front contact 8 of relay CZVS, which relay controls arm of signal R2 and remains energized after arm 0 has been restored to the stop position. As indicated in the drawing, contact 6 closes at the end of a relatively short time period which begins when device TE is released after it has been reversed to close contact to pick up relay "IEP, while contact I, on the other hand, closes when device TE is fully released at the end of a relatively long time period.

The signal relay L2H for signal L2 is controlled by a lever repeating relay LZVR, and this signal has an approach locking relay LMR which corresponds in function to relay RMR for signal R2, but the circuits for relays LZVR and LMR have been omitted in order to simplify the drawing. We have also in the accompanying drawing not shown the source of current for energizing the various relays but have shown in lieu thereof only the terminals of the source which we have identified by the references B and C to designate the supply and common return terminals of the source, respectively.

Assuming the apparatus to be in its normal condition as shown in the drawing, a circuit may be traced from terminal B, contact Ill, (closed when signal RD indicates caution or stop), back contact II of signal relay RCZH, back contact 52 of m'gnal relay RAZH, front contact 4 of track relay ATR, relay RMR to the other terminal C of the source of current. Relay RMR becomes energized over the circuit just traced and then closes its stick contact I3 bridging contact -3, so that relay RMR will remain energized as long as signal R2 remains at stop.

To clear arm a of signal R2 for an approaching high speed train, the operator moves lever RZV to the 1 position, closing a circuit which may be traced from terminal B, lever contact I4, relay R2VR to terminal C. Since switch I is normal, its normal indication circuit which may be traced from terminal B, contact I5 of the circuit controller controlled by switch machine ISM, relay INKR to terminal C, is closed,

so that relay INKR is energized. Assuming that signal L2 is at stop, its approach locking relay LMR is energized and the circuit for relay RAZH is closed, which circuit may be traced from terminal B, contact I6 of relay LMR, back contact I! of relay LZVR, front contact I3 of relay I NKR, front contact [9 of relay R2VR, back contact 20 of relay CZVS, front contacts 2I and 22 of relays ITR and INKR, relay RAZH to terminal C. Relay RA2I-I thus becomes energized to clear arm a of signal R2 and opens its back contact I2 to deenergize relay RMR, which relay upon releasing, opens contact 23 in the control circuit of relay IWR to lock switch I against operation.

When the approaching train passes signal R2, relay ITR releases, opening contact 2| to deenergize relay RAZH to put the signal to stop and to close its back contact I2 in the pickup circuit of relay RMR, which circuit is completed over back contact 3 of relay ITR so that relay RMR becomes energized. The switch, however, remains locked because contact 24 of relay ITR in the circuit for relay IWR is now open. When the train leaves section IT, relay ITR again picks up, closing the control circuit for relay IWR which may be traced from terminal B, con tacts 25, 2t, 23 and 26, relay EWR, contact 27 to terminal 0. Contacts 25 and 21 constitute a manually operable pole-changer whereby relay IWR may be energized in a direction corresponding to the position of lever IV to control the circuits for switch machine ISM as indicated in the drawing.

Assume now that switch I is reversed so that relay IRKR is energized over contact I 5, the operator may clear arm 0 of signal R2 to permit a slow speed train movement over the switch by moving lever RZV to position I to close a circuit which may be traced from terminal B, contact 28 of lever RZV, front contact 29 of relay RMR, relay CZVS to terminal C. Relay CZVS then becomes energized, and since contact I4 is also closed in position I of lever RZV, relay R2VR becomes energized, and a circuit is closed which may be traced from terminal B, front contact 30 of relay IRKR, front contacts I9 and 20 of relays R2VR and C2VS, relay RCZH to terminal C. Relay RCZH therefore becomes energized to clear arm 0 of signal R2 and opens contact II to release relay RMR to lock the switch. Relay CZVS, however, is a stick relay and will remain picked up, being now energized over its stick circuit which may be traced from terminal B, front contact 3| of relay C2VS, contact 32 of lever RZV, back contact 29 of relay RMR, relay CZVS to terminal C. Relay RCZH} is controlled independently of track relay ITR so that arm 0 will not go to stop when the approaching train enters section IT and therefore to release the locking automatically in this instance, lever R2V must be restored to its normal position it to release relays R2VR and RC2H while section IT is occupied.

Assume now that arm a of signal R2 has been cleared but that it is restored to the stop position by returning lever RZV to position 11 when a train is approaching and is occupying section AT. Relays R2VR and RAZH will then release but relay RMR does not pick up because contact 4 in its pick-up circuit is open, due to the presence of the approaching train. To release the looking, the operator reverses the time element device TE, closing contact 5 to complete a circuit which may be traced from terminal B, contacts after contact 5 opens.

H], II and l2, back.contact I3, contact 5, relay TEP to terminal C. Relay TEP picks up and closes its stick contact 33, and remains energized At the end of a predetermined time interval, contact 1 of the time element device TE closes, completing the pickup circuit for relay RMR which includes that contact and front contact 9 of relay TEP, .and then relay RMR picks up to complete its stick circuit, and opens back contact l3 to release relay TEP.

Assume next that arm 0 of signal R2 has been cleared instead of arm a, and arm 0 is then put to stop bymoving lever R2V to position 1r when a train is approaching and relay ATR is deenergized. To release the locking, the operator is required to operate the time element device TE to pick up relay TEP as before, but in this instance since relay C2VS is picked up, relay RMR becomes energized over the pickup circuit including contacts 8, 6 and 9 at the end of the relatively short time interval when contact 6 closes. Contact 8 of relay CZVS thus serves as a selector contact and causes the short time element measured by the device TE to be efiective to release the locking in lieu of the long time element, in the event the signal is manually put to stop and the operation of the device TE is initiated when relay CZVS is energized.

Assume now that arm c of signal R2 has been cleared While switch I is normal, and that traffic conditions become more favorable so that the operator desires to clear arm a. To do this, he will move lever RZV from position Z toposition 1". Relay RZVR remains energized, but contact 32 in the stick circuit for relay ,CZVS opens so that this relay releases, and its back contact 20 closes to complete the signal control circuit for clearing arm a, so that relay RAZH picks up. If lever R2V is then returned to position 11., the long time element governed by contact I of device TE is effective, and not the short time element governed by contact 6, because contact 8 of relay CZVS is open.

Assume next that with arm a of signal R2 at clear, the operator moves lever RZV from position 1' to position I to clear arm 0. Relay RlVIR. being released, its front contact 29 is open and relay C2VS does not pick up. The operator therefore must hold lever RZV in position '11 long enough to release relays RZVR and RA2H, and to pick up relay RMR, in order to clear armcwhen he moves the lever to position Z. If a train is approaching in section AT, the lever must therefore be held in position n for the duration of the long time element. It is thus clear that theoperator can not defeat the purpose of the time element device by attempting to clear arm 0 momentarily after he manually restores arm a to stop, in order to take advantage of the short time interval imposed under certain traiiic conditions when arm 0 is put to stop. After arm 0 has been cleared, of course, the short time element will be effective upon returning arm e to stop. On the other hand, our apparatus functions in such a manner that the usual progressive control of the signals is retained, so that the operator may first clear arm 0 and then clear arm a without incurring a delay. Arm (1, however, will clear only as the result of relay CEVS becoming released, so that the usual long time element will be effective when arm a is restored to stop.

It will be clear from the foregoing that these desirable results are secured by a very simple arrangement of circuits, involving an auxiliary stick relay C2VS for controlling the low speed signal apparatus.

which relay has a stick circuit arranged to hold the relay energized after the signal is restored to stop, and a pickup circuit controlled by the usual approach locking relay. Furthermore, since the apparatus of our invention may be applied without added complication to a signal governing the movement of traffic over a plurality of switches, it is clear that'it may advantageously be employed in large interlockings involving complicated track layouts. In such layouts it is often desirable to provide time locking of the opposing signals. This feature is also provided by our Thus, the circuits for relays RAZH and RC2H already traced include in part a portion of a similar circuit for the opposing signal relay L2H, which circuit may be traced from terminal B, back contact 34 of relay CZVS, front contact 35 of relay RMR, back contact I!) of relay RZVR, front contacts l8 and l I of relays INKR and LZVR, relay L2H to terminal C. It follows, therefore, that signal L2 can be cleared only when lever RZV is in position n, signal R2 indicates stop, relay RMR is energized and relay CZVS is deenergized, and that the conditions under which the relatively long or short time element will become effective upon the restoringof signal R2 to its stop position to temporarily prevent operation of the switch, as imposed by the apparatus of our invention, are also effective to prevent clearing of the opposing signal L2.

The time element delay imposed upon the clearing of the slow-speed signal after the high speed signal is put tostop, as provided by our apparatus as hereinbefore described, although desirable as a matter of general practice, in some instances may be undesirable, as for example, when arm 0 of signal R2 is employed as a train-order signal.

An arrangement of apparatus by which the effect of the time delay in question upon the signal may be avoided when it is desired to do so is illustrated in Fig. 2. This view shows a portion of the circuits of the signal relays of Fig. l, which differ from the corresponding parts of Fig. 1 in that the circuit for signal relay RAZH includes an additional contact 36 of lever RZV closed in position r, while to the circuit for signal relay RCZH has been added a by-pass around front contact 20 of relay CZVS, comprising a contact 31 of lever REV closed in position 1 and in series therewith a back contact 38 of relay RlVlR.

Assuming now that the modification shown in Fig. 2 is employed, and that with arm a of signal R2 at clear, the operator moves lever RZV from position 1 to position 1. RAZH becomes opened at contact 36 of lever REV and the circuit of relay RCZH becomes closed over contact 31 of lever RZV and back contact 28 of relay RMR so that arm av will go to stop and arm 0 will clear at once. Relays RMR. and CZVS remain deenergized, so that although in'this instance the long time element will be efiective if arm 0 is restored to stop when a train is approaching, the operator will be unable to defeat the purpose of the time element.

Although we have herein shown and described but two forms of railway traific controlling apparatus embodying our invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of our invention.

- Having thus described our invention, What we claim is:

1. In combination, a stretch of railway track The circuit of relay including a track switch, a signal indicating proceed, slow speed or stop for governing the movement of traffic into said stretch, manually .controllable means for governing the signal, locking means eifective to prevent operation of the switch for a selected time interval after the signal is manually caused to indicate stop provided there is a train approaching within a predetermined distance of the switch, a stick relay which becomes energized when said manually controllable means is operated to cause the signal to indicate slow speed, and means controlled by said stick relay when energized for shortening said selected time interval.

2. In combination, a stretch of railway track including a track switch, a signal indicating proceed, slow speed, or stop for governing the movement of traffic into said stretch, manually controllable means for governing the signal, a looking relay which when deenergized prevents operation of the switch, means for deenergizing said locking relay when the signal indicates proceed or slow speed and for a selected time interval after the signal is manually caused to indicate stop, provided there is a train approaching within a predetermined distance of the switch, and means causing the selected time interval to be relatively long or relatively short depending upon whether the signal indication is manually changed from proceed to stop or from slow speed to stop.

3. In combination, a stretch of railway track, a signal indicating proceed, slow speed or stop for governing the movement of traffic over the stretch, manually controllable means for governing the signal, a locking relay, means for deenergizing said locking relay when the signal indicates proceed or slow speed and also retaining said locking relay deenergized for a selected time interval after the signal is manually caused to indicate stop provided there is a train approaching within a predetermined distance of the signal, and means controlled by said locking relay eiiective when said manually controllable means is operated to change the indication of the signal from proceed to: slow speed to cause the signal to indicate stop instead of slow speed until said locking relay becomes energized.

4. In combination with a railway track switch, a main signal and an auxiliary signal for governing the movement of traihc over the switch, a signal lever efiective when moved from its normal position to a second position to close a contact for clearing the main signal and when moved from its normal position to a third position to close a contact for clearing the auxiliary signal, locking means eiiective when deenergized to prevent operation of the switch, means for energizing said locking means eiiective only when both signals indicate stop, a time element device controlled by the signals for delaying the energization of said locking means for a selected time interval after the lever has been restored to normal to put the auxiliary signal at stop and for a longer time interval after the lever has been restored to normal to put the main signal at stop, and means for rendering said time element device ineffective to delay the energization of the locking means when there is no train approach.- ing within a predetermined distance of the signal.

5. In combination with a railway track switch, a main signal and an auxiliary signal for governing the movement of traflic over the switch, a signal lever effective when moved from its normal position to a second position to close a contact for clearing the main signal and when moved from its normal position to a third position to close a contact for clearing the auxiliary signal, locking means effective when deenergized to prevent operation of the switch, means for energizing said locking means effective only when both signals indicate stop, a time element device controlled by the signals for delaying the energization of said locking means after the lever is restored to normal for a relatively long or relatively short time interval depending on whether the main signal or the auxiliary signal is put to stop by the operation of said lever, and means for rendering the time element device ineffective to delay the energization of said locking means provided there is no train approaching the signal.

6. In combination, a stretch of railway track, a main signal and an auxiliary signal for governing the movement of traific into said stretch, a locking relay, means for deenergizing the locking relay when either signal is cleared and for a predetermined time after signal is manually caused to indicate stop, manually operable signal control means, a signal control relay, a circuit for the signal control relay closed when said signal control means is operated to: clear either signal, a stick relay, a pickup circuit for the stick relay closed when the signal control means is operated to clear the auxiliary signal provided the locking relay is energized, a stick circuit for the stick relay effective to maintain it energized when the locking relay releases, and circuits for selectively clearing the auxiliary signal or the main signal including front contacts of the signal control relay and front and back contacts respectively of said stick relay.

7. In combination, a stretch of railway track including a track switch, a main signal and an auxiliary signal for governing the movement of trafiic into the stretch, a three-position signal lever, a signal relay and a stick relay for governing the signals, a locking relay which when deenergized prevents operation of the switch, a circuit for the signal relay closed when the lever is moved from normal to its second or third position, a pickup circuit for the stick relay including a front contact of the locking relay and closed when the lever is in its third position, a stick circuit for the stick relay including its own front contact and also including a back contact of the locking relay and contacts closed when the lever is normal or in its third position, circuits for clearing the auxiliary signal or the main signal including front contacts of the signal relay and front and back contacts respectively of said stick relay, and a circuit for controlling the locking relay when the lever is restored to normal ineluding a front contact of said stick relay.

8. In combination, a stretch of railway track including a track switch, a main signal and an auxiliary signal for governing the movement of trafiic into the stretch, a locking relay which when deenergized prevents operation of the switch, means for deenergizing said locking relay when either signal is cleared and for a selected time interval after the signal is manually caused to indicate stop under certain trailic conditions, manually operable signal control means, an auxiliary relay, a circuit for energizing said auxiliary relay controlled by said signal control means and by said locking relay, circuits closed selectively when the signal control means is operated to clear the auxiliary signal or the main signal according as the auxiliary relay is energized or deenergized, and means causing said selected time interval to be relatively short or long depending upon whether or not the auxiliary relay has been energized. e

9: In aninterlocking system for railroads, a track switch, two signals for governing the movement of traffic over'the switch, locking means rendered efiective when eitherof saidsignals is cleared to prevent operation of the switch, a

time measuring device, means including said device for releasing said locking means under certain traffic conditions at the end of a measured time interval when a signal is manually put to stop, a selector contact'which occupiesone position when one signal is put to stopand another position when the other signal is put to stop, andmeanscausing said time interval to be relatively long or relatively short, depending upon the position of said selector contact.

10. In an interlocking system for railroads, a track switch, a high speed signalv and a slow speed signal for governing the movement of traffic over the switch, manual control means for the signals, switch locking means rendered effective when either signal is cleared to prevent operation of the switch, a time measuring device for releasing said locking means under certain traffic conditions at the end of a measured time interval after a signal is manually put to stop, and a selector contact controlled by the manual control means for causing said time interval to be relatively long when the high speed signal is put to stop and to be relatively short when the slow speed signal is put to stop.

11. In combination, a stretch of railway track including a track switch, a signal indicating proceed, slow speed or stop for governing the movement of traffic .into said stretch, manual control means for said signal, locking means effective to prevent operation of the switch under certain traific. conditions for a selected time interval after the signal is manually caused to indicate stop, a selecting relay controlled by the manual control means and by said locking means, means effective when said selecting relay is energized for causing the signal to indicate slow speed when the manual control means is operated to clear the signal, and means effective if said selecting relay is energized for shortening said time interval when the manual control means is operated to cause the signal to indicate stop.

12. In an interlocking system for railroads, a track switch, a high speed signal and a slow speed signal for governing the movement of traffic over the switch, manual control means for the signals, a switch locking relay deenergized when either signal is cleared and effective when deenergized to prevent operation of the switch, a slow acting relay, a circuit for the slow acting relay closed only when the signals indicate stop, said circuit including a back contact of the locking relay, time element means eiTective to pick up said locking relay at the end of a measured time interval after the'slow acting relay has become energized, and a selector contact controlled by the manual control means for causing said time interval to be relatively long when the high speed signal is put to stop and to be relatively short when the slow speed signal is put to stop.

13. In combination, a stretch of railway track including a track switch, a main signal and an auxiliary signal for governing the movement of traffic into said stretch, a signal lever having a normal, a second and a third position, a locking relay which when deenergized prevents operation of the switch, a stick relay, a pick-up circuit for said stick relay including a front contact of the locking relay and closed when the lever is in its third position, a stick circuit for said stick relay including its own front contact and also including a back contact of the locking relay and contacts closed when the lever is in itsnormal position or in its third position, a circuit for clearing the auxiliary signal closed when the lever is in its third position provided either said stick relay is energized or the locking relay is deenergized, a circuit for clearing the main signal closed when the lever is in its second position, and a circuit for controlling the locking relay when the lever is restored to normal including a front contact of said stick relay.

in combination, a stretch of railway track including a track switch, a main signal and an auxiliary signal for governing the movement of traflic into said stretch, a locking relay which when deenergized prevents operation of the switch, means for deenergizing said locking relay when either signal is cleared and also r taining said locking relay deenergized for a selected time interval after the signal is manually caused to indicate stop under certain traffic conditions, manually operable signal control means, an auxiliary relay, a circuit for energizing said auxiliary relay controlled by said signal control means and by said locking relay, circuits closed selectively when said signal control means is operated to clear said auxiliary signal or said main signal, and means causing said time interval to be relatively long or short depending. upon whether or not said auxiliary relay has been energized.

i5. In combination, a stretch of railway track including a track switch, two signals for governing the movement of traffic into said stretch, a three-position signallever effective when moved to a first position to clear one signal and when moved to a second postion to clear the other signal, said lever being efiective when in its third position to cause both said signals to indicate stop, locking means effective to prevent operation of the switch for a measured time inter ing the movement of traffic into said stretch, a

three-position signal lever effective when moved to a first position to clear one signal and when moved to a second position to clear the other signal, said lever being eiIective when in its third position to cause both said signals to indicate stop, locking means effective to prevent operation of the switch for a measured time interval after either signal is caused to indicate stop by the operation of said lever to its third position provided there is a train approachng within a predetermined distance of the switch, and means dependent upon whether said lever has been moved to said third position from its first position or from its second position for governing the length of said measured time interval.

17. In combination with a railway track switch, a plurality of manually controllable signals including a slow speed signal for governing the movement of trafiic over the switch, locking means effective when any of said signals is manually put to stop for preventing the operation of said switch for a measured time interval, and

meansefiective when said slow speed signal is manually put to stop for shortening said measured time interval.

18. In combination, a stretch of railway track including a track switch, a main signal and an auxiliary signal for governing the movement of trafiic over said switch, manually controllable means for governing said signals, locking means for at times preventing the operation of said switch for a. measured time interval when either of said signals is manually put to stop, means controlled by said manually controllable means and by traffic conditions in said stretch for clearing said main signal, and means controlled by said manually controllable means and said locking means for clearing said auxiliary signal.

19. In combination, a stretch of railway track including a track switch, two signals at the same location for governing train movements at different speeds into the stretch, manually controllable means for governing said signals, locking means eiiective when either signal is manually put to stop for preventing the operation of said switch for a measured time interval, and means controlled by said manually controllable means for selecting the length of said measured time interval in accordance with the speed permitted by the signal last cleared.

EARL M. ALLEN. HENRY S. YOUNG. 

